This invention relates to a ramming composition for use as a temperature-stable patching and lining material in the iron and steel industry. When compared with known ramming compositions, the composition of the invention has a longer use life, exhibits increased strength, is less prone to cracking and is less hazardous to the users' health.
The ramming composition of the invention is based on a refractory material, preferably mullite, and a binder material which includes very fine silica particles dispersed in water. The preferred composition also includes smaller amounts of silicon carbide, graphite, and clay. Specifically, the preferred ramming composition includes 65-80% by weight of mullite, 5-15% by weight of silicon carbide, 2-5% by weight of graphite, 2-6% by weight of ball clay, and 5-10% by weight of the aqueous silica binder system. The foregoing components are preferably mixed to a workability of 8-15% as measured by ASTM Procedure C181-82. The resulting composition is a damp mixture which can be rammed directly to surfaces, including hot surfaces, and then dried.
The use of a silica binder represents an improvement over known ramming compositions which utilize binders based on petroleum pitch, clay and/or other organic resins. Because ramming is usually performed on hot surfaces, compositions which utilize organic binder materials often exhibit noxious fumes. Furthermore, the known compositions have a tendency to oxidize. Oxidation over a period of time severely weakens the known ramming compositions, causing them to crack, crumble and separate from the applied surfaces.
The composition of the invention, on the other hand, is nonhazardous. Furthermore, the use of a silica binder inhibits oxidation and imparts superior strength to the ramming composition of the invention.